Boat the planing bottom of which is fitted with sets of rollers for conversion of friction into dynamic thrust

ABSTRACT

Two sets of idle rollers are fixed to the planing bottom of a boat, one set on each side, or to its appendices, for transforming the continuous movement of water against the V-shaped hull, responsible for hindering its forward progress, into a propulsive thrust. This results in faster forward drive, propulsive power being equal. Each set of rollers is housed in a rectangular container placed in a purposely made recess in the stern with the rollers lying perpendicular to the forward direction of the boat. The sets of rollers can be placed separately preferably close to the stern board and to the keel. These rollers are cylindrical or frusto-conical in shape, of any diameter, length and number compatible with the size of the planing bottom of the boat, their surfaces being smooth or suitably grooved to improve thrust, stability and drainage.

FIELD OF APPLICATION OF THE INVENTION

The present invention relates to the field of pleasure boating or, more precisely, to a boat the planing bottom of which is fitted with sets of rollers for conversion of friction into dynamic thrust.

REVIEW OF THE KNOWN ART

The bottom of the boat being that part immersed in water, boats may be roughly divided into two categories according to whether the hull has a planing or non-planing bottom. Non-planing bottoms are generally those of flat boats, the planing bottoms being V-shaped so that, when the boat moves forward, its hydrodynamic reaction produces a thrust that lifts part of the hull above the surface of the water. The effect of this thrust is to reduce the submerged part of the hull, thereby reducing resistance to forward movement.

Planing bottoms are usually designed for high-speed boats and are often ribbed or grooved to optimize hydrodynamic thrust. FIG. 1, referring to patent application PCT/1998/000029, shows a boat 1 whose planing bottom 2 presents two pairs of grooves 3, 4 and 5, 6 parallel to the keel 7 symmetrical on each side of the bottom. Grooves 3, 4 and 5, 6 extend along the entire length of the hull and, during navigation, intercept the sideways flow of water to the bottom 2 so as to increase thrust and lift the hull. FIG. 2, relative to the same patent application, shows the stern board 8 of the boat 1, on the lower part of which can be seen the profiles of the four grooves 3, 4, 5 and 6. As an alternative to the grooves, the bottom 2 can be longitudinally ribbed, these ribs being known as “longitudinal skates”.

It may therefore be deduced that the main idea underlying the solution proposed by the known art referred to above, is that of exploiting the hydrodynamic thrust acting on the sides of the bottom to reduce the friction that impedes the boat's drive by lifting the hull.

GB 819411 A discloses a ship's hull with freely rotatable rollers, preferably hollows, on substantially its entire outer surface below the water line. In addition to the freely rotatable rollers on the bottom of the hull, deflectable braking flaps, independently operable on the port and starboard sides, are also positioned on the bottom of the hull of the ship. The very considerable friction which arises between the skin of the hull and the water is thus cut down to a small residual friction experienced by the rollers as they revolve, so that a substantial saving in propulsive power will be secured. Covering with rollers the whole immersed surface of the rectangular hull is a very expensive task and unsuitable to be used on fast boats, as for example those with V-shaped hulls.

EP 0265382 A discloses a floating wheel to allow the displacement of aquatic vehicles, as well as aquatic vehicles that uses said wheels. The wheels have a spherical conformation and, optionally, multiple blades project from the outer surface. The wheels are loosely affixed to an axle connected to the hull of the vehicle. The floating wheels facilitate the movement of the aquatic vessel. Alternative embodiments make use of cylindrical wheels. The dislocating wheels are suitable to be mounted on cargo ships, barge hulls, sail boats, or in alternative to funny aquatic tricycles. Said wheels, because of their floating requirement and the transversal disposal in respect of the hull, are unsuitable to be used on fast boats, as for example those with V-shaped hulls.

SUMMARY OF THE INVENTION

Purpose of the present invention is to reduce the friction between the water and the hull in boats with a planing bottom, particularly when at medium/low speed, the bow is not yet sufficiently raised from the water. To achieve this purpose, subject of the present invention is a boat comprising housing means to contain at least one set of idle rollers, one set at each side of the bottom, said rollers lying perpendicular to the forward movement of the boat and may come in contact with the water to reduce the friction between the water and the hull, in which according to the invention said bottom is of the planing type, and said housing means for each set of rollers are placed, separately one from another, preferably close to the stern board and to the keel, as described in claim 1.

Further characteristics of the present invention considered innovative are described in the dependent claims.

According to one aspect of the invention, said housing means for at least one set of rollers comprise a container fixed to the planing bottom of the boat, said container having no wall opposite to the planing bottom so that the rollers may come in contact with the water. The wall of said housing nearest to the stern board is preferably concave to favour outflow of water from the housing, so lessening resistance to the boat's forward movement.

The housing means for each set of rollers, can be separately placed at any position between the prow and the stern board.

According to another aspect of the invention, each housing means is fitted into its respective recess in the planing bottom of the boat.

In an alternative form, the sets of rollers are fixed to the centreboard situated low down on the bottom of sailing boats.

In another alternative form, the sets of rollers are fixed to the flaps at the sides of the stern board

According to one aspect of the invention, the rollers are separated by a short reciprocal distance, in relation to their diameter, for example, by a distance of five tenths of a millimetre.

According to another aspect of the invention, the rollers are of a frusto-conical shape to favour adaptation to that of the hull.

According to another aspect of the invention, the rollers are smooth.

According to another aspect of the invention, the surfaces of the rollers are suitably grooved to improve dynamic thrust, stability of the boat and drainage.

According to another aspect of the invention, the rollers are arranged in a double row.

ADVANTAGES OF THE INVENTION

The hydrodynamic friction created during navigation is less than that produced by an ordinary boat with planing bottom without rollers. This reduction in friction is equivalent to additional hydrodynamic thrust so that, propulsive power provided by the boat's motor being equal, forward movement is faster.

The effect created by the rollers partly cancels out that of suction caused by movement of water against the hull which, when the boat is moving, increases the crushing effect of the bottom of the hull.

A further advantage is that of squatting at the inner side of the planing bottom while veering.

SHORT DESCRIPTION OF THE FIGURES

Further purposes and advantages of the invention will be made clear by the following detailed description of an example of its realization relating to a boat with a planing bottom, and by the attached drawings given purely for explanatory purposes and in no way limitative, wherein:

FIG. 1 is a view in perspective of a hull with a planing bottom with longitudinal grooves according to the known art;

FIG. 2 is a view of the rear of the hull in FIG. 1;

FIG. 3 is a side view of a boat realized according to the present invention;

FIG. 4 is a view from below of the boat in FIG. 3;

FIG. 5 is a view in perspective of a housing for the rollers in FIGS. 3 and 4;

FIG. 6 is a view in perspective of one of said rollers;

FIG. 7 is a view in perspective of a support for said rollers;

FIG. 8 is a view in perspective of a set of rollers in their seats made in the supports shown in FIG. 7;

FIG. 9 is a view in perspective of the set of rollers in FIG. 8 when in the housing seen in FIG. 5.

DETAILED DESCRIPTION OF SOME PREFERRED WAYS OF REALIZING THE INVENTION

In the following description, identical parts that appear in different figures can be marked with the same symbols. In explaining a figure reference may be made to parts not expressly shown in that figure but in a preceding figures. The scale and proportions of the parts shown are not the real ones.

With reference to FIG. 3, a boat 10 will be seen, on the visible side of whose bottom 11 there is a rectangular container 12 placed in a recess made to receive it. The container 12 has no wall on the side opposite to the bottom of the boat, and is so placed that its long sides are parallel to the keel 13. The container 12 houses a set of rollers 14 laid parallel to the shorter side of container 12. Said container is fixed to the bottom 11 close to the stern board 15 and to the keel 13. The figure shows that the rollers 13 lie perpendicular to the forward direction of the boat 10 and are in contact with the water.

With reference to FIG. 4, it will be noted that in a second recess, made in the bottom 11 of the boat, there is a second container 16 exactly like container 12 in relation to the line of the keel 13. The second container 16 houses a set of rollers 17.

With reference to FIG. 5, the rectangular container 12 (or identically 16) is shown, bordered at a right angle on three sides to form the seat for the rollers, the fourth side 20 at the rear (nearest to the stern board) being curved to favour outflow of water. An “L”-shaped border on the outer boundary connects the container 12 to the edges of the recess made in the bottom 11 of the hull.

With reference to FIG. 6, this shows the cylindrical roller 14 (or identically 17) from whose ends two coaxial pins 21 and 22 project. The surface of roller 14 may be smooth or grooved to improve its thrust, its stability and its drainage. As an alternative to cylindrical rollers, use may be made of frusto-conical rollers of any diameter, length and number.

With reference to FIG. 7, a support 23 will be noted that includes ball bearings 24 to form seats for inserting pins 21 or 22 for rollers 14 and 17. The bearings 24 are aligned one with another and sufficiently spaced to allow for idle rotation of the rollers 14 and 17.

With reference to FIG. 8, sets of rollers 14 will be seen sustained by supports 23. The diameter and length of each roller 14 vary according to the characteristics of the bottom 11 to which they are fixed; the same applies to the number of rollers and the distance between them.

With reference to FIG. 9, the set of rollers 14 will be noted sustained by their respective support 23 inside the container 12.

In one practical example of its realization, the hull has a planing bottom 11, 5.5 m long, and rollers 14 and 17 placed at a reciprocal distance of five tenths of a millimetre. The performance of the boat 10 in the practical example has been compared with that of a boat without rollers. Both boats carried an outboard 40 CV engine operating at 5,600 revolutions per minute. The boat without rollers reached a speed of 24.6 nautical miles per hour, measured with GPS, while the practical example of a boat with rollers reached 29.9 nautical miles per hour. The experiment therefore showed that, revolutions of the engine shaft being equal, the presence of the rollers made it possible to increase speed by 5.3 nautical miles per hour, with much faster acceleration and immediate planing, quicker veering (less squatting on the inside of the veer).

Based on the description given of a preferred example of its realization, it is clear that some changes may be made by an expert in the field without thereby departing from the ambit of the invention, as will appear from the following claims. 

1-11. (canceled)
 12. Boat (10) comprising housing means (12, 16) to contain at least one set of idle rollers (14, 17) on each side of the bottom (11), said rollers lying perpendicular to the forward movement of the boat (10) and may come in contact with the water reducing the friction between the water and the hull, characterized in that said bottom (11) is of the planing type, and said housing means (12, 16) for each set of rollers (14, 17) are placed, separately one from another, preferably close to the stern board (15) and to the keel (13).
 13. Boat (10) as in claim 12, wherein said housing means (12, 16) comprise a container fixed to the bottom (11), said container having no wall on its side opposite to the bottom.
 14. Boat (10) as in claim 13, wherein the wall (20), of said container (12, 16), nearest to the stern board (15), is concave to favour outflow of water.
 15. Boat (10) as in claim 12, wherein said housing means (12, 16) are each fitted into a respective recess in the bottom (11).
 16. Boat (10) as in claim 12, wherein said rollers (14, 17) are frusto-conical in shape for better adaptation to the bottom of the boat.
 17. Boat (10) as in claim 12, wherein the surface of said rollers (14, 17) is smooth.
 18. Boat (10) as in claim 12, wherein the surface of said rollers (14, 17) is grooved.
 19. Boat (10) as in claim 12, wherein said rollers (14, 17) are arranged in a double row.
 20. Boat (10) as in claim 13, wherein said housing means (12, 16) are each fitted into a respective recess in the bottom (11).
 21. Boat (10) as in claim 14, wherein said housing means (12, 16) are each fitted into a respective recess in the bottom (11). 